Self-powered photodetector based on the PEDOT:PSS/Ga2O3 organic–inorganic hybrid heterojunction

Solar-blindness is an essential requisite for detection of UV-C radiation in daylight condition, e.g. detectors of flames, corona discharge in electrical power lines, monitoring possible UV-C radiation reaching earth due to ozonosphere reduction; monitoring of UV-C sources for sterilization and air purification. The Ga2O3 semiconductor family (five polymorphs with bandgap ranging from 4.7 to 5 eV) has attracted much interest for photodetection of UV-C radiation. This is well documented in the literature, in particular for the thermodynamically stable β and the κ polymorphs (see e.g. [1]). The latter is thermally stable up to about 700 °C and easy to deposit on commercial low-cost substrates thanks to its greater crystalline symmetry (orthorhombic vs. monoclinic) and lower growth temperature compared to  Ga2O3. In this work, the architecture of a hybrid heterojunction based on a n-type κ-Ga2O3 layer, and a heavily p-doped PEDOT:PSS will be presented and discussed, with focus on the geometry of the device and the physical features of the p- and n- materials, with the aim of opening the path towards an optimized structure. The self-powered operation is demonstrated for interdigitated planar structures (sketch in Figure 1), where the n-type κ-Ga2O3 is deposited by MOVPE on Al2O3 substrate, and the p-type organic layer is deposited by 3D printing (Figures 2 and 3). These results will be compared with those earlier reported for full inorganic UV-C photodetectors based on κ-Ga2O3 [2-3]. We want to stress that the development of self-powered photodetectors is of great interest, because they can operate independently, sustainably, without energy consumption. In this context, the use of hybrid heterojunctions makes the fabrication of the device even more cost-effective and simple. [1] C. Wu F. Wu H. Hu S. Wang A. Liu, and D. Guo Materials Today Physics 28, 100883 (2022) [2] C. Borelli A. Bosio A. Parisini M. Pavesi S. Vantaggio, and R. Fornari Mater. Sci. Eng. B 286, 116056 (2022). [3] A. Parisini, P. Mazzolini, O. Bierwagen, C. Borelli, K Egbo, A. Sacchi, M. Bosi, L. Seravalli A., Tahraoui, and R. Fornari, J. Vac. Sci. Technol. A 40, 042701 (2022).